<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <style>
        .fa{
            width: 200px;
            height: 200px;
            background-color: #f00;
        }
        .fa:hover{
            background-color: aqua;
        }
        .fa:checked{
            background-color: #0f0;
        }
    </style>
    <div class="fa">
        <div class="so"></div>
    </div>
    
</body>
</html>